One of the men behind the biohazard outbreak, and always seen with his signature shades on. Wesker possesses knowledge about biological engineering and used to be an agent for Umbrella. He was planted in S.T.A.R.S. to spy on them and was even made their commanding officer.

Wesker took particular note of Chris and his combat prowess while in charge of the team. He is cold-blooded and has no qualms about betraying the people who place their faith in him. He betrayed and killed Marcus, lured S.T.A.R.S. into the mansion and nearly wiped them out, and even pretended to be dead to join Umbrella's rival company.

Wesker was the one who sent Ada Wong to retrieve the G-virus and was involved in the incidents at Rockfort Island. He appears intent on gathering as much data as possible on viral weaponry. Since injecting himself with a virus during the events at the mansion, his power has grown far beyond that of a normal human being.